package org.bouncycastle.crypto.params;

import java.math.BigInteger;

import org.bouncycastle.crypto.CipherParameters;

public class DHParameters implements CipherParameters {
    private static final int DEFAULT_MINIMUM_LENGTH = 160;

    // not final due to compiler bug in "simpler" JDKs
    private BigInteger g;
    private BigInteger p;
    private BigInteger q;
    private BigInteger j;
    private int m;
    private int l;
    private DHValidationParameters validation;

    private static int getDefaultMParam(int lParam) {
        if (lParam == 0) {
            return DEFAULT_MINIMUM_LENGTH;
        }

        return lParam < DEFAULT_MINIMUM_LENGTH ? lParam
                : DEFAULT_MINIMUM_LENGTH;
    }

    public DHParameters(BigInteger p, BigInteger g) {
        this(p, g, null, 0);
    }

    public DHParameters(BigInteger p, BigInteger g, BigInteger q) {
        this(p, g, q, 0);
    }

    public DHParameters(BigInteger p, BigInteger g, BigInteger q, int l) {
        this(p, g, q, getDefaultMParam(l), l, null, null);
    }

    public DHParameters(BigInteger p, BigInteger g, BigInteger q, int m, int l) {
        this(p, g, q, m, l, null, null);
    }

    public DHParameters(BigInteger p, BigInteger g, BigInteger q, BigInteger j,
            DHValidationParameters validation) {
        this(p, g, q, DEFAULT_MINIMUM_LENGTH, 0, j, validation);
    }

    public DHParameters(BigInteger p, BigInteger g, BigInteger q, int m, int l,
            BigInteger j, DHValidationParameters validation) {
        if (l != 0) {
            if (l >= p.bitLength()) {
                throw new IllegalArgumentException(
                        "when l value specified, it must be less than bitlength(p)");
            }
            if (l < m) {
                throw new IllegalArgumentException(
                        "when l value specified, it may not be less than m value");
            }
        }

        this.g = g;
        this.p = p;
        this.q = q;
        this.m = m;
        this.l = l;
        this.j = j;
        this.validation = validation;
    }

    public BigInteger getP() {
        return p;
    }

    public BigInteger getG() {
        return g;
    }

    public BigInteger getQ() {
        return q;
    }

    /**
     * Return the subgroup factor J.
     * 
     * @return subgroup factor
     */
    public BigInteger getJ() {
        return j;
    }

    /**
     * Return the minimum length of the private value.
     * 
     * @return the minimum length of the private value in bits.
     */
    public int getM() {
        return m;
    }

    /**
     * Return the private value length in bits - if set, zero otherwise
     * 
     * @return the private value length in bits, zero otherwise.
     */
    public int getL() {
        return l;
    }

    public DHValidationParameters getValidationParameters() {
        return validation;
    }

    public boolean equals(Object obj) {
        if (!(obj instanceof DHParameters)) {
            return false;
        }

        DHParameters pm = (DHParameters) obj;

        if (this.getQ() != null) {
            if (!this.getQ().equals(pm.getQ())) {
                return false;
            }
        } else {
            if (pm.getQ() != null) {
                return false;
            }
        }

        return pm.getP().equals(p) && pm.getG().equals(g);
    }

    public int hashCode() {
        return getP().hashCode() ^ getG().hashCode()
                ^ (getQ() != null ? getQ().hashCode() : 0);
    }
}
